Zk学习笔记——创建节点
参考:从Paxos到Zookeeper分布式一致性原理和实践
使用的zk依赖是cdh5.16.2的3.4.5
1 2 3 4 5 6 | <!-- zookeeper --> <dependency> <groupId>org.apache.zookeeper< /groupId > <artifactId>zookeeper< /artifactId > <version>3.4.5-cdh5.16.2< /version > < /dependency > |
Zk在创建节点的有同步创建和异步创建,但是Zk是不支持递归创建节点,即父节点必须存储。
在创建同名的节点的时候,会抛出NodeExistsException异常。
Zookeeper节点内容只支持字节数组(byte[])
同步创建节点代码,其中创建了一个永久节点,key是/app1,value是123
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | package com.bigdata.zookeeper; import org.apache.zookeeper.*; import java.util.concurrent.CountDownLatch; public class ZkExample implements Watcher { public static CountDownLatch connectedSemaphore = new CountDownLatch(1); public static void main(String[] args) throws Exception { ZooKeeper zk = new ZooKeeper( "master:2181" , 5000, new ZkExample()); System.out.println(zk.getState()); try { connectedSemaphore.await(); String path = zk.create( "/app1" , "123" .getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); System.out.println( "success create znode: " + path); } catch (InterruptedException e) { System.out.println( "Zk session established" + e); } } @Override public void process(WatchedEvent watchedEvent) { System.out.println(watchedEvent); if (Event.KeeperState.SyncConnected == watchedEvent.getState()) { connectedSemaphore.countDown(); } } } |
输出,使用Zkui查看zk中的数据,能发现多出了/app1的节点,节点的值是123
Zk中节点的类型分为持久节点(PERSISTENT),持久顺序节点(PERSISTENT_SEQUENTIAL),临时节点(EPHEMERAL),临时顺序节点(EPHEMERAL_SEQUENTIAL)
区别如下
异步创建节点代码,
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | package com.bigdata.zookeeper; import org.apache.zookeeper.*; import java.util.concurrent.CountDownLatch; public class ZkExample implements Watcher { public static CountDownLatch connectedSemaphore = new CountDownLatch(1); public static void main(String[] args) throws Exception { ZooKeeper zk = new ZooKeeper( "master:2181" , 5000, new ZkExample()); System.out.println(zk.getState()); try { connectedSemaphore.await(); zk.create( "/app2" , "123" .getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT, new IStringCallback(), "This is context" ); Thread. sleep (Integer.MAX_VALUE); } catch (InterruptedException e) { System.out.println( "Zk session established" + e); } } @Override public void process(WatchedEvent watchedEvent) { System.out.println(watchedEvent); if (Event.KeeperState.SyncConnected == watchedEvent.getState()) { connectedSemaphore.countDown(); } } } class IStringCallback implements AsyncCallback.StringCallback { @Override public void processResult(int i, String s, Object o, String s1) { System.out.println( "Create path result : [" + i + ", " + s + ", " + o + ", real path name : " + s1); } } |
如果创建成功,返回的状态码是0
如果节点已经存在,返回的状态码是-110
具体介绍
本文只发表于博客园和tonglin0325的博客,作者:tonglin0325,转载请注明原文链接:https://www.cnblogs.com/tonglin0325/p/13251364.html
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